The present invention relates to a friction material for brakes or clutches for use in automobiles, railroad vehicles, industrial machines, and so on.
Generally, as shown in U.S. Pat. No. 4,226,759, U.S. Pat. No. 4,273,369 and so on, a friction material (brake pad, brake lining, clutch facing or the like) for brakes or clutches is composed of reinforcing fibers such as organic fibers, inorganic fibers, metal fibers, etc.; a bonding material of thermosetting resin such as phenolic resin or the like; a friction modifier such as metal particles, ceramic particles, rubber particles, cashew dust or the like; and additonal elements such as a solid lubricant and a filler. In most cases, conventionally, metal fibers such as copper fibers or the like and metal particles such as copper particles or the like have been used in combination as the reinforcing fibers and the friction modifier in order to have a sufficient friction coefficient and stable friction performance to the friction material. In the case of using such metal fibers and metal particles, however, there is a tendency of generating noises of low frequency while the friction coefficient and the friction performance are improved.